Never a dumb question. When sizing the case, the distance from the shoulder or datum line to base of the case is headspace, its letting you know how much room is left between the head of the case & the bolt face. Over All Length, is the measurement from the head of the case to the tip of the bullet. Not the most accurate measurement but when loading into a magazine or chamber, its standard for the firearm to operate. Ogive measurement let's you know the amount or space to the rifling. Hope I helped.

If any thought had ever been put into a term to describe the distance from the rifling to the bolt face the information would be available from Sinclair and or Hornady. I make tools that allows me to transfer the measurement to a seating die, I call the tool a transfer; I know that is not very catchy but once I know the distance from the rifling to the bolt face I am not required to start over the next day.

We can talk about the tools that are made for measuring the distance from the beginning of the rifling to the bolt face. Most of the tools are made to be bullet friendly meaning the tools have radiuses instead of sharp edges. My tools imprint on the bullet.

I list both the case and chamber because that is what SAAMI does. Then there are reloaders that speak where SAAMI is silent. SAAMI does not identify head space for the case but reloaders managed to purchased case head space gages even thought 60 + years ago L.E. Wilson started selling case length gages complete with instructions dated 1954.

Well, I ain't laughing! I started reloading in 1969 and I can't answer your question. I've done it a few times, and used the Hornady tools designed for the job, but I don't have a clue of the correct term...

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What SAAMI does not use is the ogive for any measurement. OAL is measured from the pointy bit to the flat bit of the cartridge.
The ogive is on a different part of nearly every bullet type with the same weight. Look at the .224" 55 grain bullets from Sierra.https://www.sierrabullets.com/produc...lets/rifle.cfm
"...C.B.T.O. at .177 diam..." Is at least a standard. Isn't used by anybody, but it's a standard.
"...SAAMI does not identify head space for the case..." That's because headspace is a rifle manufacturing tolerance only. Cartridges do not have headspace.
"...60 + years ago..." 62. Last March. snicker.

Well this turned into a good thread. Someone was explaining all the measurements. I appriciate the time you took to do that but I completely understand all the measurements and how they are taken and I have all the tools to take the measurements.

I use the Hornady bullet comparator that goes on your calipers to take this measurement and the Hornady headspace comparator to check my head space. I use the Hornady OAL gauge to find my max OAL length and use the bullet comparator to take the measurement.

Then when I start working up loads for a gun I will then step back and load 5 shells to test at each length off the lands in .005" increments. .005", .010", .015", .020", and .025" to find out if the gun likes the bullet close to the lands or more bullet jump. Although a lot of bolt action rifles with a lot of throat wear the max OAL won't actually be the real max OAL because the cartridge won't fit in the magazine because the actual OAL is to long. So sometimes my max C.B.T.O. for certain rifles is simply the max length that the magazine will function with.

I was just curious if there was a proper term for this measurement from the back of the case to the bullets Ogive. As I said I personally for my own notes write these measurements down as B.S.O.A.L. For what I call the Bullet Shoulder(ogive) O.A.L.

I was just curious if there was a actual universal term for this measurement so that when discussing bullet seating lengths on this forum with everyone; people would know what I was talking about. I assumed or thought for sure their would be a definite term for this. It sounds like maybe the actual term is C.B.T.O for Cartridge Base To Ogive?!?

SAAMI gives maximum and minimum measurements for case manufacture. That is all chamber specs do. I consider headspace the matching of the two. Without the standardization of the cartridge case, chamber headspace would be meaningless. The chamber specs actually dictate where the ammunition manufacturers place the ogive of the bullet. Some may fall way short of the rifling, but no loaded SAAMI spec ammo will exceed that point. You will just have a lot of "Freebore".

Duncan74
Looks like no one really answered the question. I guess what ever works for you to reference your notes is best. For me when I read just the initials, its like trying to figure whats on car vanity plates. I just wright the whole thing out. If it doesn't rain in the morning, I'll be trying some jump rounds. Be Safe. Chris

The bullet has an ogive, somewhere along the ogive the bullet contacts the rifling meaning the chamber does not have an ogive.

Quote:

I use the Hornady bullet comparator that goes on your calipers to take this measurement and the Hornady headspace comparator to check my head space. I use the Hornady OAL gauge to find my max OAL length and use the bullet comparator to take the measurement.

Back to calling everything a head space tool and everything having head space. The Hornady tool is a comparator, if you measure before and again after you have just about mastered the comparator. The case does not have head space. Back to the Wilson case gage, it is a datum based tool, the complicated part about the Wilson case gage with a datum is the way they ZEROED the tool; Hornady has never caught on to that concept, the same goes for reloaders.

You are missing a measurement; I am the fan of transfers, I transfer the measurement from the chamber to the seating die. I know that makes no sense to anyone but I do not need the Hornady tool nor do I need to measure the length of the case from the rifling contact point on the bullet to the bolt face.

The case has the chamber's specs as a dimension guide line. You could load a few of the wrong cartridges in a rimmed chamber and still pass the chamber headspace specs. The chamber DOES have a dimension to agree with the ogive on a bullet and bullet diameter. That little angle you grind on forward of the freebore varies with different cartridges. I suspect the angle helps the bullet stay concentric with the barrel because it agrees with the curve of the ogive.

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